Periodontal disease is a chronic infection of the periodontal ligament of teeth which plagues a major portion of the general population. Plaque accumulation triggers inflammation of the marginal gingiva. If the inflammation is permitted to persist, the gingivitis can worsen to become periodontitis. As a response to the presence of bacteria, lytic enzymes such as collagenase accumulate at the site. This inflammatory process causes destruction of the collagen matrix and the inserted gingival fiber apparatus. Repeated infection and neglect result in the periodontal ligament being slowly destroyed. With the destruction of the periodontal ligament follows the resorption of bone surrounding the affected teeth. With continued infection of the periodontal ligament, ligament destruction, and bone resorption, little viable bone tissue remains to support the tooth. The overall result is the formation of a pocket around the tooth. This progressive disease ultimately leads to the loss of the affected tooth unless treatment is obtained. No current treatment is effective in regenerating the lost bone around the tooth. As a result, the permanent bone defect is a haven for plaque and bacteria that cause periodontal disease so that recurrence is common.
There are many technical approaches to periodontal therapy but the infrabony defect remains the Nemesis for the periodontist. Recently there has been an escalated effort in the direction of regenerative periodontal therapy with the ultimate goal of stimulating bone growth, regeneration of a functional periodontium at the site of the pocket, and the reattachment of epidermal and connective tissues. Successful therapy will require a larger degree of predictability and reproducibility than is currently available. The unpredictability of bone and periodontum regeneration is the limiting factor in regenerative therapy.
Autogenous bone transplants are commonly used for regenerative therapy since some new bone regeneration is frequently observed. The disadvantage is that a second surgical procedure is required to obtain the transplant material. This requires more time, expense to the patient, a more complicated procedure, and the final results are less than desired. Allografts are more advantageous since an unlimited amount of material is available and a second operation is not required. Demineralized allogenic bone matrix (DABM) is another natural biomaterial being used clinically for osseous reconstruction. In general, all bone grafts, regardless of the type, elicit the same type of repair response and are of limited success (Barrington, 1981; Stahl, 1977; Haggerty, 1977; Urist, 1965).
It is very desirable to have man-made materials that can be used in place of tissue grafts. There are no problems with immune response, the material can be readily prepared and can have a very long shelf life. Unfortunately, most biomedical engineering materials do not enhance bone formation and have a history of limited success.
A number of materials containing biocompatible calcium phosphate have been developed. The first of these contain primarily calcium and phosphrous compounds. Search of the prior art reveals the following calcium-phosphate based biocompatible implant materials disclosed in the following patents:
Driskell, Heller and Koenigs (U.S. Pat. No. 3,913,229 issued Oct. 21, 1975) disclosed dental methods and materials for use in treating diseased or traumatized teeth and periodontal tissues and is especially suitable for endodontic (pulp caping, root canal, and tooth replanting techniques) treatments of teeth. The materials utilized are the physiologically compatible and soluble calcium phosphate compounds, whitlockite and brushite. These materials consist entirely of calcium phosphate compounds. The material is prepared into a porous agregate paste or powder and positioned adjacent to the calcified tissue. The particles are a small size such that the putty like mixture exhibits colloidal properties.
Niwa et. al. (U.S. Pat. No. 4,497,075 issued Feb. 5, 1985) disclose a material for filling defects or hollow portions of bone tissues. The material is a crystalline calcium phosphate apatite compound with the calcium to phosphate ratio in the range of 1.33 to 1.95.
Jarcho (U.S. Pat. No. 4,097,935 issued July 4, 1978) discloses a new process for manufacturing polycrystalline ceramics of pure hydroxylapatite and a material consisting of a mixture of hydroxylapatite and whitlockite with molar ratios of calcium to phosphorus in the ranges of 1.57 to 1.67. The material is to be used as a filter in dental cements and as a dental and surgical prosthetic material. Jarcho (U.S. Pat. No. 4,207,306 issued June 10, 1980) also discloses a process for producing polycrystalline ceramic oxides.
Ebihara et. al. (U.S. Pat. No. 4,113,500 issued Sept. 12, 1978) disclose a process for forming by molding and sintering a hydroxylapatite powder also containing magnesium. The object has high mechanical strength and is reported to be biocompatible. It is proposed to be suitable for a medical implant materials such as prosthetic teeth or bones.
Guillemin et. al. (U.S. Pat. No. 4,356,572 issued Nov. 2, 1982) disclosed a biodegradable bone implant composed of resorbable calcium carbonate. The implant is to be used an the form of a filler or replacement part for bone.
Takami and Kondo (U.S. Pat. No. 4,308,064 issued Dec. 29, 1981 and U.S. Pat. No. 4,376,168 issued Mar. 8, 1983) disclose a calcium phosphate ceramic containing yittrium oxide which improves the mechanical properties. It is considered a strong and biocompatible material.
In the alveolar bone environment around teeth implants, these types of materials (including tricalcium phosphate and hydroxylapatite) do not produce the extent of bone regeneration that is desirable. The ultimate result is similar to that with bone implants. The results remain far from the desired correction of the periodontal pocket. This may be partially due to the fact that this material does not bond to bone by the same mechanism as the surface active ceramic used with the current process.
Controlled surface active ceramics have been developed over the past decade and are known to the art. These materials consist of four primary constituents with the general composition 40 to 60 weight percent silicon dioxide, 10 to 35 weight percent sodium oxide, 15 to 45 weight percent calcium oxide, and 6 weight percent phosporus pentoxide. This general composition range is represented by FIG. 1. Two of the primary ingredients are calcium oxide and phosporus pentoxide. These are selected in proportions such that the Ca/P ratio is similar to that for hydroxyapatite bone mineral. Sodium ions are added to the composition in the form of sodium oxide in order to flux the molten glass batch, aid glass formation, and stabilize the local aqueous environment of the surrounding tissues. These three constituents are held in glassy form by silicon dioxide which serves as a network former decreasing the solubility rate of the other ions. Other constituents may also be present in small amounts. The material may be either amorphous or crystallized ceramic. A particularly preferred composition of the prior art contains 45 weight percent silicon dioxide, 24.5 weight percent sodium oxide, 24.5 weight percent calcium oxide, and 6 weight percent phosphorus pentoxide. This composition is commonly designated as 45S5 (Hench et. al., 1971; Hench and Paschall, 1973; Hench et al. 1977, Hench and Ethridge 1982).
Other controlled surface active ceramics are known to the art including the silicate based biocompatible implant materials disclosed in the following patents:
Broemer et. al. (U.S. Pat. No. 3,981,736 issued Sept. 21, 1976 and U.S. Pat. No. 3,922,155 issued Nov. 25, 1975) disclosed a new biocompatible glass ceramic material containing 20 to 60 weight percent silicon dioxide, 5 to 40 weight percent phosphorus pentoxide, 2.7 to 20 weight percent sodium oxide, 0.4 to 20 weight percent potassium oxide, 2.9 to 30 weight percent magnesium oxide, and 5 to 40 weight percent calcium oxide, and 0.5 to 3.0 weight percent fluorine. This composition (containing magnesium oxide) makes a better glass ceramic because of its crystallization characteristics. They also disclose a crystallization process including times and temperatues of nucleation and crystallization.
Hench and Walker (U.S. Pat. No. 4,171,544 issued Oct. 23, 1979) discloses a new biological material. The material is capable of forming a strong bond with bone due to the high specific surface area developed in a silica rich surface layer on the implant material. Examples of compositions include glasses and glass ceramics with more the 80 weight percent silicon dioxide and inorganic cements such as Portland cement. Calcium, phosphorus, and sodium are not necessary ingredients for the strong bond with bone.
Yagi (U.S. Pat. No. 4,366,253 issued Dec. 28, 1982) disclose another composition and process for producing a glass ceramic with a much lower melting temperature. This composition contains 8 to 48 weight percent (silicon dioxide and germanium dioxide), 8 to 35 weight percent phosphorus pentoxide, 3 to 18 weight percent boron oxide, 16 to 28 weight percent alumium oxide, and 8 to 33 weight percent of (calcium, magnesium, strontium, and barium oxide). The specific times and temperatures of crystallization are disclosed.
Controlled surface active materials are characterized by their ability to form a strong direct chemical bond with living bone in vivo. This type of material has been shown to exhibit a number of changes in vivo. The ceramic's surface activity produces an amorphous gel on the surface into which collagen fibers become embedded. Subsequent heterogeneous hydroxylapatite nucleation and crystallization within the gel proceeds by an ectopic process. This bridges the gap between the bulk glass and the calcium phosphate rich surface. The silicon in this surface gel may be similar in some respects to that which procedes hydroxylapatite mineralization during normal bone growth. Simultaneous to this reaction, hydronium ions are removed from the surrounding fluids by an ion exchange process increasing the local solution pH. The surface pH of 10 developed by glass surface is also similar to the pH (9.4) at which amorphous calcium orthophosphates begin to rapidly precipitate and may be close to the pH present in vivo at regions of high osteoblastic activity. As a result new bone is deposited on the material surface and the material becomes incorporated into the surrounding bone. Implantation of the ceramic into bone defects results in a chemical bond between the ceramic and the bone. This is in significant contrast to single oxide ceramics (silicon dioxide, alumina, magnesium oxide, etc.), metals (stainless steel, Co-Cr alloy), or polymers (acrylic bone cement) which simply fall out of the bone defect during histological preparation or sectioning. No other known nonresorbable material including tricalcium phosphate and hydroxylapatite have consistently shown this type of consistent direct bonding to bone. The overall conclusion is that controlled surface active ceramics play an active role during in vivo ossification.
Other related aspects of the prior art have concentrated on efforts to achieve better attachment of bulk implant devices to bone using two approaches. These include porous coatings on implant devices into which bone is to grow and surface active coatings on the surface of implant devices to which bone attaches.
The prior art reveals several approaches to coatings of biocompatible glass or glass-ceramics onto metallic or ceramic implant bodies, as disclosed in the following patents:
Heimke and Henicke (U.S. Pat. No. 3,919,723 issued Nov. 18, 1975 and U.S. Pat. No. 4,031,571 issued June 28, 1977) disclose a design of a metallic or dense ceramic joint implant and a processes for coating the implant with a bioactive substance such as calcium-aluminum phosphate.
Hench and Greenspan (U.S. Pat. No. 4,103,002 issued July 25, 1978) disclose a process for coating a bioglass onto dense aluminum oxide ceramic implants. The process includes at least two layers of bioglass.
Scharbach et. al. (U.S. Pat. No. 3,987,499 issued Oct. 26, 1976) disclose a metallic hip joint design and a metallic vertebra prosthesis with an enamel coating.
Hench and Buscemi (U.S. Pat. No. 4,234,972 issued Nov. 25, 1980) disclose a process for coating bioglass onto metallic implants. The process allows the coating of a metal with a glass of dissimilar thermal expansion coefficient.
Ogino et. al. (U.S. Pat. No. 4,424,037 issued Jan. 3, 1984) discloses a dental implant design coated with a biologically active glass or glass ceramic coating.
Prior art also reveals several approaches to the use of porous coatings on implants to achieve attachment to bone tissues.
Inukai and Fukuda (U.S. Pat. No. 4,371,484 issued Feb. 1, 1983) disclose a method for producing porous hydroxyapatite.
Tomonaga and Aoki (U.S. Pat. No. 4,222,128 issued Sept. 16, 1980) disclosed a composite material consisting of a mixture of sintered apatite and a polymer resin. The composite is reported to have controlled biocompatibility with bone as well as possessing excellent strength.
Heide et. al. (U.S. Pat. No. 4,309,488 issued Jan. 5, 1982) discloses an implant material consisting of a metallic body with a coating into the surface of resorbable calcium phosphate particles. When the particles dissolve out of the surface in vivo, tissue grows into the pores left behind in the implant.
Draenert (U.S. Pat. No. 4,373,217 issued Feb. 15, 1983) discloses another mixture of ceramic and polymer for use as a prosthetic material. The mixture consists of methacrylate (and/or acrylate) and resorbable tricalcium phosphate. The resorbable ceramic reportedly dissolves permitting tissue to attach to the porous material.
Hench and Walker (U.S. Pat. No. 4,171,544 issued Oct. 23, 1979) disclose a new biological material. The material is capable of forming a strong bond with bone due to the high specific surface area developed in a silica rich surface layer on the implant material. Examples of compositions include glasses and glass ceramics with more than 80 weight percent silicon dioxide and inorganic cements such as Portland cement. Calcium, phosphorus, and sodium are not necessary ingredients for the strong bond with bone.
It is therefore an object of this invention to provide controlled surface active material which may be used to treat and repair general bone resorption and bone damage caused by disease.
It is a second object of this invention to provide controlled surface active ceramic material in granular form wherein the granules are of optimum size and shape to achieve optimum results im treating and repairing general bone resorption and bone damage caused by disease, particularly periodontal disease.
It is another object of this invention to provide a method of treatment of general bone resorption and bone damage adjacent to teeth which is caused by periodontal disease.
It is still another object of this invention to provide a method of restoring a portion of the alveolar ridge in order to provide a anatomical structure upon which traditional dentures may be seated.
It is yet another object of this invention to provide a method of filling defective sockets in alveolar bone after tooth extraction.